This invention is applicable to the field of optical telecommunications and can be applied to all semiconductor lasers and in particular to lasers with an alloy III-V single or double heterostructure. For example, this may involve, but not exclusively, GaAs, GaAlAs, InGaAs, GaAsP, InGaAsP, InP lasers, etc.
Within the field of optical telecommunications, there currently exists a need to obtain laser sources offering extremely good frequency stability. It is only via this condition that it is possible to implement radioelectricity techniques, such as modulation, demodulation, etc.
The frequency stabilization of lasers in general and semiconductor lasers in particular is a technique widely known in current applications. Several solutions have been proposed: automatic ocntrol of the frequency at a resonannce mode of a Fabry-Perot standard or at an absorption line of a gas, synchronization on another laser with the latter being stabilized, etc.
So as to render it easier to obtain this stability, the laser to be stabilized is selected or modified so as to already possess a certain frequency stability. It is thus possible to operate by sorting double heterostructures so as to only retain those components whose alloy makes it possible to obtain the desired central frequency; it is also possible to reduce the actual transmission width by extending the resonant cavity by means of an external auxiliary mirror (optical counter-reaction); finally, it is possible to resort to a diffraction grid disposed along the active zone (known as a "Distributed Feed-Back or "DFB" laser or as a "Distributed Bragg Reflection" or DBR" laser).
This state of the art is described, for example, in the article of Motoichi OHTSU and entitled "Frequency Stabilization in Semiconductor Lasers" published in the "Optical and Quantum Electronics" journal, vol. 20, (1988), pages 283-300.
However, these known techniques have a certain number of drawbacks. The method for sorting heterostructures results in low production yields. Resorting to the external mirror optical counter-reaction poses difficult mechanical problems and results in having structures which are complex and heavy to use. As regards lasers with grids distributed along the active zone, these may only be obtained at the price of significantly complicating production methods due to epitaxy reruns.